Dimerization of conjugated dienes with pi-allyldinitrosyliron complexes



Int. Cl. C07c 11/16, 3/18 US. Cl. 260-666 7 Claims ABSTRACT OF THE DISCLOSURE Dimerization of conjugated dienes by contact with a catalyst comprising ir-allyldinitrosyliron complexes of germanium, tin and lead.

This is a divisional application of my copending application having Ser. No. 576,821, filed Sept. 2, 1966, now Patent No. 3,448,129 issued June 3, 1969.

This invention relates to a novel catalyst, and to a dimerization process employing said catalyst. In one of its aspects, the invention relates to new complex ar-allylic compounds of iron.

In another aspect, the invention relates to the dimerization of unsaturated hydrocarbons in the presence of a catalyst comprising complex vr-allylic compounds of iron.

In another aspect, the invention relates to the homodimerization of acyclic conjugated dienes containing up to about 12 carbon atoms per molecule by contacting said dienes with the complex catalyst of this invention.

In another aspect, the invention relates to the codimerization of two different conjugated dienes by contacting these compounds with a complex catalyst comprising complex vr-allylic compounds of iron.

In another aspect, the invention relates to the essentially quantitative production of 4-vinylcyclohexene by contacting 1,3-butadiene with the complex catalyst of this invention at temperatures substantially lower than those required to dimerize, 1,3-butadiene without a catalyst.

Numerous catalysts have been proposed to dimerize conjugated dienes such as 1,3-butadiene, to higher molecular weight cyclic unsaturated compounds such as 4-vinylcyclohexene. For example, the reaction of 1,3-butadiene takes place very slowly at ambient temperatures without a catalyst while at temperatures above 100 C. the conversion is rapid and accompanied by higher molecular weight polymerization products. It is an object of this invention to provide a new dimerization process and a catalyst therefor which can be used at moderate temperatures to produce essentially quantitative yields, that is, without formation of other polymeric by-products. A further object of the invention is to provide a long lasting catalyst for homoand co-dimerization processes. It is a particular object of the invention to provide a catalyst, and a process employing said catalyst, for the formation of vinylcyclohexene from 1,3-butadiene in high yields at moderate temperatures.

Other aspects, objects, and the several advantages of the invention will be apparent to one skilled in the art from studing the specification and claims.

In accordance with the invention, a new composition of matter is provided having the formula:

wherein (CHR-CRCH is an allylic radical 1r-bonded to the iron atom and in which R is hydrogen or a methyl radical; M is one of tin, lead, or germanium; and X is one of chloride, bromide, iodide, or a a-bonded hydrocarbon radical preferably having up to 20 carbon atoms.

United States Patent ice The a-bonded hydrocarbon radicals are aliphatic or cycloaliphatic or aromatic. Examples are: allyl, phenyl, benzyl, 4-tolyl, 4-methyl-6-heptynyl, cyclopentyl, 12-eicosenyl, and 2-naphthyl. Said complex composition of matter has particular utility as a catalyst for the dimerization of conjugated dienes.

As used herein, the term dimerization refers to homodimerization of acyclic conjugated dienes, and to the co-dimerization of two different acyclic conjugated dienes.

A specific example of the novel complex compounds of this invention is bis(1r-allyldinitrosyliron)tin dichloride whose structure is believed to be (Note: represents 1r-bonded allyl radical.)

Another novel catalyst composition is bis(1r-allyldinitrosyliron) allyltin chloride whose structure is believed to be I NO L Ll Other examples of the novel compounds provided by this invention include:

bis (vr-allyldinitrosyliron germanium 'dibromide bis ('ir-IHGiLhfillYldillilIO syliron germanium dichloride bis (vr-crotyldinitrosyliron) tin diiodide bis (1r-allyldinitrosyliron) lead dichloride bis [11'- Z-methylcrotyl) dinitrosyliron] lead dibromide bis(1r-methallyldinitrosyliron)tin chloride bromide bis (vr-allyldinitrosyliron) methyl tin bromide bis(ar-methallyldinitrosyliron)phenylgermanium chloride bis(ar-crotyldinitrosyliron)benzyllead iodide bis [1r- (Z-methylcro tyl dinitrosyliron] 4-tolyltin chloride bis (1r-allyldinitro syliron) 4-methyl-6-heptynyllead bromide bis (1r-allyldinitrosyliron cyclopentyltin chloride bis(qr-methallyldinitrosyliron) 12-eicosenyltin chloride bis (1r-allyldinitrosyliron)Z-naphthylgermanium iodide.

The method of preparing these novel compositions broadly comprises reacting ,u,p.-dihalotetranitrosyldiiron (the dimer of dinitrosyliron halide) and an allyl or substituted allylmetal or halide compound. These compositions can be prepared by several methods:

METHOD A Under an inert atmosphere, an equimolar mixture of pf-dihalotetranitrosyldiiron (halo-chloro, bromo, or iodo) and an allyl, methallyl, crotyl, or 2-methylcroty1 compound of tin, germanium, or lead is mixed in the presence of any suitable inert diluent, preferably an inert hydrocarbon such as benzene. Any order of addition can be used, as well as any convenient temperature and pressure, room temperature and atmospheric pressure being convenient. It is preferred that the mixture be allowed to stand at least one hour after the initial mixing before it is used in a catalytic reaction. During the standing period a fine precipitate may settle out. This may be removed, if desired, for convenience by centrifugation or filtration.

The catalytic solution is somewhat air and moisture sensitive and should be kept under an inert atmosphere. It

3 should be used within a few days of its preparation for best results.

If desired, the catalytic compound can be isolated from the above solution by conventional crystallization techniques. The isolated and dried solid is relatively stable to the atmosphere and has a considerably longer shelf life than its solution.

METHOD B Under an inert atmosphere, 1 mole of ,,u.-dihalotetranitrosyldiiron (as above), 1 mole of tin, germanium, or lead dihalide (chloride, bromide, iodide), 2 moles of allyl, methallyl, crotyl, or 2-methylcrotyl chloride, bromide, or iodide, and at least 4/3 mole of Al powder (or its equivalent in other reducing metals, such as powdered Zn, Fe, Mg, or reducing compounds such as cobaltocene) are mixed, in any order, in the presence of any suitable inert solvent, tetrahydrofuran being particularly suitable. After mixing the solution is stirred, preferably for several hours under any convenient conditions such as room temperature or higher. The solution is then used as the solution of Method A.

METHOD C Under an inert atmosphere are mixed 1 mole of pb,fL -dihalotetranitrosyldiiron, 2 moles of powdered tin, germanium, or lead metal, and 2 moles of an allylic halide (as above) in an inert solvent such as tetrahydrofuran. After a suitable reaction period, 1-10 hours at room temperature for example, the solution is used as the solution of Method A.

METHOD D Under an inert atmosphere are mixed 2 moles of Roussins black salt KFe S (NO) (or 3 moles of Roussins red salt [Fe(NO) SEt 6 moles of cadmium halide, 3 moles of a tetrallylic tin, germanium, or lead compound, and at least 3 moles of powdered zinc or its equivalent of another reducing agent such as powdered aluminum, sodium borohydride, cobaltocene, and the like. The mixing is continued until the catalyst formation is substantially complete, about 1-10 hours at room temperature for example. After the reaction period, the solution is used as in Method A. (A ,u,,u'-dihalote-tranitrosyldiiron or a derivative is believed to be an intermediate in this preparation.)

METHOD E To prepare the cataytic compounds having a hydrocarbon radical a-bonded to the tin, germanium, or lead atom, one mole of the products obtained from Methods A through D (whether isolated solid or in solution) is treated with 1-2 moles of hydrocarbyl magnesium halide or a hydrocarbyl alkali metal, alkaline earth metal, or aluminum compound. The treatment is carried out in any suitable solvent, such as the ethers or hydrocarbons previously mentioned, at temperatures generally lower than room temperature. After a reaction time of at least about one hour, the solution can be used in a catalytic process or the catalytic composition can be isolated by crystallization. Both the solution and isolated solids are preferably protected from the atmosphere and both the solution and solid should be utilized within a few days.

The ,u, .t'-dihalotetranitrosyldiiron reagents used in the above synthesis techniques can be prepared by any conventional method known in the art. A particularly convenient procedure is that described in copending Ser. No. 518,018, filed Jan. 3, 1966. If desired, the preparation of the ,,u-dihalotetranitrosyldiiron compound and the complex 1r-allylic iron compounds of the present invention can be sequentially prepared in the same vessel and in the same solvent without isolation of the former.

Method A has been used to synthesize some of the novel compounds of this invention: For example, by contacting ,u,;t'-dichlorotetranitrosyldiiron with tetrallyltin in the 4 presence of benzene, his(1r-allyldinitrosyliron) tin dichloride is formed. By treating this compound with allylmagnesium bromide (Method E), bis(1r allyldinitrosyliron) allyltin chloride is formed.

As an example of Method B, ,1t, .'-dibromotetranitrosyldiiron is contacted with powdered aluminum metal in the presence of lead (II) chloride and methallylchloride to give bis(methallyldinitrosyliron)lead dichloride. When this compound is contacted with phenylsodium, bis(methallyldinitrosyliron)phenyllead chloride is obtained.

As an example of Method C, t,M-dichlorotetranitrosyldiiron is mixed with powdered germanium and crotyl bromide in the presence of tetrahydrofuran, resulting in the production of bis(1r-crotyldinitrosyliron)germanium dibromide. Treatment of this compound with butyllithium results in the production of bis(1r-croty1dinitrosyliron) butylgermanium bromide.

As an example of Method D, KFe S (NO) is mixed with tetraallyltin, cadmium iodide, powdered zinc, and sodium borohydride in ethyl ether to produce a solution containing bis(1r-allyldinitrosyliron)tin diiodide.

The conjugated dienes to which this process is directed include those acyclic conjugated dienes having up to about 12 carbon atoms per molecule, or mixtures thereof. Some specific examples of these are: 1,3-butadiene, isoprene, piperylene, 2,3-dimethylbutadiene-1,3, 1,3-hexadiene, 2,4-octadiene, 2-methylpentadiene-1,3, 4-ethy1decadione-1,3, and the like.

According to the dimerization process of this invention, the conjugated diene is contacted with the catalyst at a temperature within the range of from about 0 to about C., preferably 20-60 C. The conttact can be carried out either batchwise or continuously using any conventional contacting apparatus. In batch reactions, the catalyst mixtures can be prepared either in the reaction vessel before the addition of the conjugated diene or in a separate vessel and then pumped to the dimerization vessel. The dimerization can be carried out at any convenient pressure which is sufficient to maintain a substantially liquid state. Pressures ranging from 0 to about 1,000 p.s.i.g. can be used. The contact time will vary according to the efficiency of the contacting technique, the reaction temperature, and the desired degree of conversion, but will generally be in the range of from about 1 minute to about 10 hours, preferably 30-90 minutes. The catalyst usage will be in the range of from about 0.001 to 10, preferably 0.01-1 millimole of iron per mole of conjugated diene. Diluents, such as ethers and inert hydrocarbons, can be used in the reaction zone but the reaction is preferably carried out substantially in the absence of substantial amounts of diluent.

After completion of the reaction, the dimeric products are recovered by any conventional technique such as by fractionation, crystallization, adsorption, and the like. If desired, the crude reaction product can be treated first with an aqueous inorganic acid to destroy and/or remove the catalyst.

The invention can be further illustrated by the following examples.

EXAMPLE I Preparation of his (ar-allyldinitrosylironfiin dichloride The title compound was prepared by mixing 4 ml. of a tetrahydrofuran solution of u, .dichlorotetranitrosyldiiron, 10 ml. dry benzene, 1.0 ml. of tetraallyltin, and 0.25 ml. thiophene. After standing for several days, the mixture was centrifuged to remove inorganic solids which had precipitated and then cooled to 78 C. to produce orange crystals. Recrystallization from warm toluene gave about 0.75 g. of crystals, M.P. 132 C. with decomposition. In other runs, it was found that the thiophene could be omitted without affecting the results.

Elemental analysis calculated for C H Cl Fe N O Sn showed the following:

Calculated for C H C1 Fe N O SnC, H,

Cl, 14.08; Fe, 22.18; N, 11.12; Sn, 23.62; mol. wt., 1 503.7. Found: C, 14.7; H, 2.2; Cl, 14.4; Fe, 23.1; N, 10.7; Sn, 21.7; mol. wt., 487.

The tetrahydrofuran solution of the n,,u'-dichlorotetranitrosyldiiron reagent used in the above synthesis was prepared by treating a mixture of 16 g. (0.1 mole) of anhydrous ferric chloride and g. iron powder under nitrogen with 65 ml. of tetrahydrofuran. The resulting reaction mixture was stirred at a high speed for minutes and heated externally as needed to maintain reflux. During this time the yellow ferric chloride was reduced to gray ferrous chloride. After addition of 65 ml. of dry benzene, nitric oxide was bubbled through the refluxing mixture at a rate of 0.25 l/min. for 90 minutes. The solution was then cooled and stored under nitrogen at 5 C. The solution of l-dichlorotetranitrosyldiiron contained about 2.4 mil limoles dissolved iron per ml. Only about percent of the iron, however, was in the form of the ,u,p.'-dichlorotetranitrosyldiiron compound, the remaining iron being in the form of soluble by-products of the catalyst forma tion.

The infrared spectrum of this material is consistent with the indicated structure of this compound and shows that the allyl groups are ar-bonded to the iron atom.

EXAMPLE 11 Preparation of bis(1r-allyldinitrosyliron)tin dichloride (Method B) Preparation of bis(1r-allyldinitrosyliron)tin dichloride (Method C) The catalyst solution was prepared by stirring, at room temperature and under a nitrogen atmosphere for 3-5 hours, a mixture of 4.0 ml. of the .t,,u.'-diChl0l0t6tfaI1l* trosyldiiron solution (from Example I), 10 m1. of dry tetrahydrofuran, 1.0 g. of powdered tin metal, and 0.75 ml. allyl chloride. After standing several hours, the deep orange soltuion was centrifuged to remove inorganic solution of 20 g. of sodium hydrosulfide in 200 ml. of water. A solution of 80 g. of ferrous sulfate heptahydrate with a drop of sulfuric acid in 600 ml. of water was then poured slowly into the heated solution. After heating in a hot Water bath (85-90 C.) for 30 minutes, the mixture was filtered hot, 10 ml. of 30 percent potassium hydroxide solution was added and it was allowed to stand at room temperature for 20 hours. The black crystals were re covered by filtration and recrystallized from acetone and dried for 24 hours over tridecylaluminum, yielding about 8 grams.

EXAMPLE V Preparation of bis(wr-allyldinitrosyliron)allyltin chloride (Method B) Orange crystals of bis(1r-allyldinitrosyliron)tin dichlo ride prepared in Example I were treated with an equimolar amount of allylmagnesium bromide at 78 C. The orange crystals which were crystallized from this mixture were isolated and found to have infrared absorption bands for both w-allyliron and allyltin groups. An elemental analysis which was carried out on this compound agreed with the empirical formula C H ClFeN O Sn indicating that one chlorine of the original molecule had been replaced with an allyl group to give bis(1r-allyldinitrosyl iron)allyltin chloride.

EXAMPLE VI Dimerization of 1,3-butadiene to 4-vinylcyclohexane Butadiene-1,3 was dimerized to 4-vinylcyclohexene (VCH) using catalysts of the present invention with essen tially a quantitative ultimate yield (no by-products were detected) in a number of batch runs carried out in 100- 500 ml. stirred glass reactors immersed in a 40 C. water bath. Part of the total butadiene charge, generally about 350 g., was present in the reactor initially and the rest was added as the reaction proceeded. The reaction was virtually complete in about 2 hours when the catalyst was added in the form of the solution in which it was originally prepared. When the catalyst was added in the form of its isolated solid crystals, the reaction, which was carried out at room temperature in this case, took longer (about 24 hours) apparently due to the lower temperature and the time required for complete catalyst solution.

The following table shows the results obtained using several catalysts of the present invention for the dimerization of 1,3-butadiene.

TABLE I.CATALYTIC DIMERIZATION OF BUIADIENE CATALYST SYSTEM Productivity,

Run No. Catalyst Preparation Quantity mole Fe 1 I 03115 (N0)zFe]2SnClz Soln. of Example I 0.3 mmole ram. 570 2 [(0 11 (N0)2Fe]2SnO12 cr ystalllzed solid of Example 73.6 mg 870 3 [(03135) (N0)2F6]2CaH5 nC1 2, 500

Crrstallized solid of Example 3.1 mg

solids and was then found active for dimersization of bu tadiene.

EXAMPLE IV Preparation of bis (vr-allyldinitrosyliron)tin dichloride (Method D) 1 Molecular weight.

The foregoing data illustrate that the invention catalyst and process are not only very selective, but they are also capable of producing 4-vinyl-cyclohexene from 1,3-butadiene in very high yields based on the amount of catalyst used.

EXAMPLE VII Dimerization and co-dirnerization of other conjugated dienes Using the same general procedure described in Example 'VI, isoprene was dimerized, piperylene was dimerized, and a mixture of isoprene and butadiene were codimerized using, as a catalyst, a solution of the bis(1rallyldinitrosyliron)tin dichloride prepared in Example I. The results of these tests are shown in the following table.

1,4dimethyl-4-viny1cyclohexene.

EXAMPLE VIII Continuous preparation of 4-vinylcyclohexene Butadiene was dimerized to 4-vinylcyclohexene in a continuous process using the catalyst as prepared in Example II. The reactor was tubular being constructed from a 20 foot length of OD stainless steel tubing which was Wound into a coil and immersed in a tem- 'perature controlled oil bath. The reactor was fed by means of a pump, from an ice-chilled tank containing a prepared mixture of butadiene and catalyst. All portions of the reactor were dried and flushed with dry benzene before and between runs of the test. A pressure of 450 p.s.i.g. was maintained during the runs.

Table III shows a tabulated summary of the results of these runs.

8 I claim: 1. A process of dimerization comprising contacting at least one conjugated diene with a complex catalyst having the formula:

wherein (CHRCR-CH is an allyl radical 7rbonded to the iron atom and in which R is selected from hydrogen and a methyl radical, M is selected from tin, lead, and germanium, and X is selected from chloride, bromide, iodide, and a 'y-bonded hydrocarbon radical.

2. A process as defined in claim 1 comprising contacting two different acyclic conjugated dienes.

3. A process as defined in claim 2 comprising contacting isoprene and piperylene with bis(1r-allyldinitrosyliron)tin dichloride.

4. A process as defined in claim 1 wherein the temperature is in the range of from about 25 to about 100 C.

5. A process as defined in claim 1 wherein said conjugated diene is 1,3-butadiene.

6. A process as defined in claim 5 wherein said complex catalyst comprises bis(1r-allyldinitrosyliron)tin dichloride.

7. A process as defined in claim 5 wherein said com- TABLE IIL-PRODUCTION OF 4-VINYLOYCLOHEXENE IN CONTINUOUS REACTOR Productivity, kg.

Run Butadiene, Temp., Residence VCH/g.

N 0. Catalyst g. 0. time, hr. mole Fe 7 2.4 mmoles Fe (catalyst 290 2 90 soln. of Example I).

8 0.6 mmoles Fe (catalyst 270 1 360 soln. of Example I) 9 0.6 mmoles Fe (catalyst 228 1 soln. of Example I).

and 'a' process utilizing this composition as a catalyst for the dimerization of conjugated dienes.

plex catalyst comprises bis(1r-allyldiriitrosyliron)allyltin chloride.

References Cited UNITED STATES PATENTS 3,448,129 6/1969 Maxfield. 3,436,431 4/1969 Cardlin et a1. 3,377,397 4/1968 Maxfield.

DELBERT E. GANTZ, Primary Examiner V. OKEEFE, Assistant Examiner 

